Taste, especially the spice, is the last thing to be judged. You need a good looking presentation,i.e. color, glaze, etc. Next thing is smell. That rib goes under a nose before it hits the teeth. Texture is next in line. Ribs should slice without coming apart, but gently pull cleanly off the bone. A little bark is good but it should be tender, not tough or dry. Spice is next. Don't kill the judges with cayenne but don't give them fruit as well. Balance in your rub plays a big part here and your rub needs to compliment your sauce too.
How many entries can you have? Might be a good idea to try a few different recipes if you can do 3 entries...
Good luck and keep us updated...